Light developable direct print silver halide compositions containing phosphonium salts

ABSTRACT

PHOTOGRAPHIC SILVER HALIDE COMPOSITIONS COMPRISING AT LEAST 10 MG. PER MOLE OF SILVER OF A PHOSPHONIUM SALT OF THE FORMULA:   (ROH)4P$Z$   WHEREIN R IS AN ALKYL GROUP AND Z IS AN ANION. IN ONE ASPECT OF THIS INVENTION DIRECT-PRINT COMPOSITIONS COMPRISING SAID PHOSPHONIUM SALTS HAVE IMPROVED PHOTOGRAPHIC SPEED AND IMPROVED IMAGE DENSITIES.

United States Patent Ofice Patented June 1, 1971 3,582,345 LIGHT DEVELOPABLE DIRECT PRINT SILVER HALIDE COMPOSITIONS CONTAINING PHOS- PHONIUM SALTS Clarence E. McBride, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed Apr. 3, 1968, Ser. No. 718,340

Int. Cl. G03c 1/28 US. Cl. 96-107 6 Claims ABSTRACT OF THE DISCLOSURE Photographic silver halide compositions comprising at least 10 mg. per mole of silver of a phosphonium salt of the formula:

wherein R is an alkyl group and Z is an anion. In one aspect of this invention direct-print compositions comprising said phosphonium salts have improved photographic speed and improved image densities.

wherein R is an alkyl group and wherein Z is an anion.

In making various print-out and direct-print silver halide compositions considerable emphasis is placed on finding various silver halide compositions with improved photographic properties, i.e., such as speed and increased image density.

It is an object of this invention to provide new photographic compositions.

It is another object of this invention to provide new print-out and direct-print compositions having increased speed.

It is another object of this invention to provide directprint and print-out compositions having increased image density.

It is still another object of this invention to provide new photographic elements.

It is still another object of this invention to provide a new process for forming image records.

I have now found that these and other objects of the invention can be accomplished by utilizing in a silver halide composition at least 10 milligrams per mole of silver of a phosphonium salt of the formula:

(ROH P Z wherein R is an alkyl group and Z is an anion. In one embodiment direct-print compositions containing from about 1 mole percent to about 2 moles per mole of silver of said phosphonium compound have improved photographic speed and increased D The improved photographic properties achieved by use of said phosphonium salt and especially by use of large amounts of said phosphonium salts are quite unexpected. It is known that certain phosphonium salts act as antifoggants; but it is quite unexpected that both photographic speed and improved image density could be obtained in direct-print or print-out emulsions.

- Phosphonium compounds useful according to this invention have the formula:

wherein each R represents an alkyl group which can be the same or a different alkyl group, substituted or unsubstituted, and Z represents any anion which does not exhibit a deleterious effect in a photographic system. Preferably R represents a lower alkyl group such as methyl, ethyl, propyl, or butyl and Z represents anions such as nitrate, perchlorate, halides, e.g., chloride bromide, iodide, etc.

The phosphonium salts can be generally employed in amounts greater than 10 mg. per mole of silver to provide improved photographic properties in silver halide systems according to this invention. Preferably concentrations of at least about 1 mole percent to about 2 moles per mole of silver are utilized in the silver halide compositions.

Preferred compounds falling within the above formula are tetrakis(hydroxymethyl)phosphonium salts and tetrakis(hydroxyethyl)phosphonium salts. Examples of these salts are tetrakis(hydroxymethyl)phosphonium chloride (THPC manufactured by Hooker Chemical Company) and tetrakis(hydroxyethyl)phosphonium chloride. The latter compound can be obtained by the procedure described in Messenger and Engles, Ber. 21: 326 (1888). The general equation for the production is 4CH CHO+HCl+PH (CH CHOH).,P Cl Suitable silver halides which can be used according to this invention include silver bromide, silver bromoiodide,

silver chlorobromide, silver chlorobromoiodide and the like. The preferred compositions are those wherein the halide of the silver is predominantly bromide. In a typical embodiment, the preferred compositions are direct-print silver halide compositions having higher internal sensitivity than surface sensivitiy as described by Hunt in Photographic Science and Engineering, vol. 5, No. 2, March- April, 1961, pp. 104-108. For a description of suitable compositions, reference is made to Davey et al., US. Pat. 2,592,250, issued Apr. 8, 1952; US. Pat. 3,206,316; Porter et al., US. Pat. 3,206,313; Sutherens, British Pat. 1,096,- 053; Kitze, Belgium Pat. 689,515 issued Jan. 13, 1967; Glafkides, Photographic Chemistry, vol. 1, pp. 31-32, Fountain Press; London; and in McBride, US. Pat. 3,- 271,157 issued Sept. 6, 1966, and US. Pat. 3,287,137.

In one preferred embodiment the silver halide compositions are direct-print compositions which contain halogen acceptors. Generally, suitable halogen acceptors are compounds which enhance the photolytic yield (as determined by radiographic analysisfor example) and/ or the photolytic density of a print-out emulsion. Typical halogen acceptors useful in the present compositions include those disclosed in McBride, US. Pat. 3,287,137; McBride, US. Pat. 3,271,157; and Kitze, US. Pat. 3,241,- 971. In one preferred embodiment nitrogen containing halogen acceptors according to the McBride patents, above, are utilized in the emulsions. In another preferred embodiment the halogen acceptors are of the type disclosed in Kitze, US. Pat. 3,241,971, which contain mercaptan groups and especially the heterocyclic mercaptans and thiones.

The compositions of the invention are generally made with a slight excess of halide ion present over that necessary initially to precipitate all of the silver halide in the preparation thereof. Preferably, water soluble iodides are added to the composition after its precipitation but before it is coated. More generally, about .1 to 50 mole percent and preferably about 0.5 to 10 mole percent of Water-soluble iodide based on the silver halide in the composition are added to the subject emulsions. Typical water-soluble iodides include the ammonium, calcium, lithium, magnesium, potassium, and sodium salts.

The silver halide compositions of this invention can be sensitized with various dyes. Typical dyes are disclosed in McBride, US. Pat. 3,287,136; Brooker, U.S. Pats. 1,846,301 issued Feb. 23, 1932, 1,846,302 issued Feb. 23, 1932, and 1,942,854 issued Jan. 9 .1934; White, US. Pat. 1,990,507 issued Feb. 12, 1935; Brooker and White,

U.S. Pats. 2,112,140 issued Mar. 22, 1938, 2,165,338 issued July 11, 1939, 2,493,747 issued Ian. 10, 1960 and 2,739,964 issued Mar. 27, 1956; Brooker and Keyes, U.S. Pat. 2,493,748 issued Jan. 10, 1950; Sprague, U.S. Pats. 2,503,776 issued Apr. 11, 1950, and 2,519,001 issued Aug. 15, 1950; 'Heseltine and Brooker, U.S. Pat. 2,666,- 761 issued Jan. 19, 1954; Heseltine, U.S. Pat. 2,734,900 issued Feb. 14, 1956; Van Lare, U.S. Pat. 2,739,149 issued Mar. 20, 1956; British Pat. 450,958 accepted July 15, 1936, and elsewhere in the literature.

The sensitizing amount of the spectral sensitizing dyes utilized can be widely varied. The concentration of the dyes will vary according to the type of composition and according to the effect desired. The suitable and most economical concentration for any given composition will be apparent to those skilled in the art upon making the ordinary tests and observations customarily used in the art of emulsion making. Generally about 1 to 1000 mg. of dye per mole of silver halide in the composition are utilized. About .05 to 1 mole percent of sensitizing dye based on the silver halide in the composition is a typical working range. A single dye or combinations of several dyes can be used in the present compositions for spectral sensitization.

Merocyanine spectral sensitizing dyes are preferably utilized in the compositions of the invention as any stain imparted to compositions containing such dyes is substantially bleached or made colorless during photodevelopment. Also, merocyanine dyes tend to be less easily displaced or desorbed from the silver halide crystals of the compositions of the invention than cyanine dyes by many halogen acceptors that are utilized in light-developable, direct-print silver halide emulsions.

Various colloids can be used as vehicles or binding agents in preparing the silver halide compositions of this invention. Satisfactory colloids which can be used for this purpose include any of the hydrophilic colloids generally employed in the photographic field, including, for example, gelatin, colloidal albumin, polysaccharides, celdescribed in Heiland, U.S. Pat. 2,580,427, issued Ian. 1, 1952, high intensity visible light, x-radiation and the like, to form a latent image in the composition of the photographic element, and thereafter the resulting latent image is photodeveloped by overall exposure of the emulsion to a radiation source of lower intensity than the original exposure, such as to a conventional fluorescent light, light from incandescent lamps commonly used for general illumination, or even ordinary daylight. Generally, the latent image formed in the composition in the first instance is not visible and does not become visible until photodevelopment. Heat is desirably utilized during the photodevelopment step. Typically the subject compositions are heated to a temperature of about 90 C. to 200 C. for about 1 to 30 seconds and photodeveloped after the initial high intensity exposure.

The invention can be further illustrated by the following examples.

EXAMPLE 1 A silver bromochloride (95 mole percent bromide, 5 mole percent chloride) emulsion is prepared according to Example 8 of McBride U.S. Pat. 3,271,157 issued Sept. 6, 1966 except that 1,8-dihydroxy-3,6-dithiooctane was used as the thioether. After preparation of the emulsion mole percent of tetrakis (hydroxymethyl)phosphonium chloride per mole of silver is added to a portion of the emulsion and it is then coated on a paper support and dried. Another portion is coated as a control.

The samples are exposed in a Honeywell Visicorder oscillograph with a galvanometer reading of 120 cycles per second and at a paper transport speed of inches per second.

Portions of the samples are photodeveloped (for the time specified in the following table) to 60 foot-candles of fluorescent light. Another portion of each respective sample is exposed imagewise, as above, and then held in contact with a heated surface at 100 C. and simultaneously photodeveloped for a few seconds to a 1000 footlulose derivatives, synthetic resins such as polyvinyl comcandle fluorescent light source.

Photodevelopment time I. AD= max.'- min.

pounds, including polyvinyl alcohol derivatives, acrylamide polymers and the like. In addition to the above hydrophilic colloids, the vehicle or binding agent can also contain hydrophobic colloids such as dispersed polymerized vinyl compounds, particularly those which increase the dimensional stability of photographic materials. Suitable compounds of this type include water-insoluble polymers of alkyl acrylates or methacrylates, acrylic acid, sulfoalkyl acrylates, or metharcylates, and the like.

The above-described compositions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include glass, metal, paper, polyolefin-coated paper, cellulose nitrate film, cellulose acetate film, polystyrene film, polyester films such as polyethylene terephthalate film, heat resistant polymeric films such as high temperature polyester, polyimide, polycarbonate films, and the like.

In forming a photodeveloped image with a typical photographic element containing a direct-print composition comprising the phosphonium salts of this invention, the photographic element is initially exposed to a relatively short duration and high intensity source of electromagnetic radiation (e.g., at least about .1 foot-candle second at an intensity of more than about 100 footcandles) such as a high intensity light source rich in blue and ultraviolet light such as are used in oscillographs It is apparent that the phosphonium salts increased the image density in each instance. Moreover, the samples containing the phosphonium salts exhibited images at least 20% quicker in each instance upon photodevelopment.

Similar results are obtained when tetrakis(hydroxyethyl) phosphonium chloride is used in the emulsion.

EXAMPLE 2 An emulsion is prepared according to Example 1 and then divided into portions. Samples were treated respectively with 1.0 mole percent, 10 mole percent, 20 mole percent, 40 mole percent and mole percent of tetrakis (hydroxymethyl)phosphonium chloride per mole of silver. A control sample was prepared which did not contain any of said phosphonium salt.

The respective samples are exposed and developed as described in Example 1. In each instance the samples containing said phosphonium salts exhibited significantly increase Dmax and substantially improved speed when compared with the control sample.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as set forth in the appended claims.

Iclaim:

1. A light developable direct-print silver halide emulsion according to claim 2 wherein said phosphonium salt is a tetrakis(hydroxymethyl)phosphonium salt.

2. A light developable direct-print silver halide emulsion comprising at least 10 mg. per mole of silver of a phosphonium salt of the formula:

wherein -R is a lower alkyl group and Z is an anion.

3. A light developable direct-print silver halide emulsion according to claim 2 comprising silver halide grains having a predominant amount of sensitivity internal to said grains.

4. A light developable direct-print silver halide emulsion according to claim 2 wherein said silver halide is precipitated in the presence of lead ions.

5. A photgraphic element comprising the emulsion of claim 2.

References Cited UNITED STATES PATENTS 4/1964 Brown et al 96-50X 6/1969 Bacon et al. 96-407 NORMAN G. TORCHIN, Primary Examiner R. E. FICHTER, Assistant Examiner US. Cl. X.R. 

